Am I being hacked?

I have been getting a lot of messages sent from my Bigpond account stating the following:

"This Message was undeliverable due to the following reason:Each of the following recipients was rejected by a remote mail server.The reasons given by the server are included to help you determine why each recipient was rejected.Recipient: <hatzis.ess@gmail.com>Reason: 5.1.1 The email account that you tried to reach does not exist. Please try 5.1.1 double-checking the recipient's email address for typos or 5.1.1 unnecessary spaces. Learn more at 5.1.1 http://support.google.com/mail/bin/answer.py?answer=6596 ru9si5757024pbc.78 – gsmtpPlease reply to <Postmaster@mx.bigpond.com> if you feel this message to be in error."

The problem is that I don't know anyone with the e-mail address hatzis.ess@gmail.com and I as sure as hell haven't been sending messages to this person.Interestingly enough, when I google hatzis.ess@gmail.com, I come to another post on Whirlpool Forums with a similar problem: /archive/2122002

Re: Am I being hacked?

It does seem strange that your email is sending to that specific address. If you haven't already I would suggest resetting the email password. Also, check over the forwarding settings in the email, it can sometimes have other emails listed, on-forwarding emails.